The application described herein relates generally to gas turbine engine components, and more specifically to a bearing assembly and a method of assembling a bearing assembly.
Gas turbine engines typically include a fan rotor assembly, a compressor, a combustor, and at least one turbine. The fan rotor assembly includes a fan with an arrangement of fan blades that radially extend outward from a rotor shaft. The compressor may compress air, which may then be mixed with fuel and funneled into a combustion chamber where the mixture may be ignited to generate hot gases, which may then be directed to the turbine. The turbine uses the hot gases to power the compressor, and/or to power the rotor shaft and the fan to propel an aircraft in flight.
The rotor shaft is typically supported by a plurality of damper bearing assemblies. Known damper bearing assemblies include a plurality of spring fingers attached between a mounting flange and a bearing housing. During normal engine operation, the damper bearing assembly acts to retain the rotor shaft's axial position and also acts to provide radial damping of the fan/rotor system. A traditional design approach includes an axial spring finger housing combined with a radial squeeze film oil damper that is able to withstand relatively small unbalance load situations. A spanner nut is used to clamp the bearing into the spring finger housing. During these normal operating conditions, the squeeze film damper bearing requires clearance in all directions around the bearing (axial and radial) for dynamic operation. However, in a potential failure mode of a liberated fan blade, relatively high radial loads combined with relatively high overturning moments may result in damage to gas turbine engine components. The radial load closes the damper gap and creates a harmonic drive effect that loads the spring fingers in torsion. The overturning moment creates high axial loads on the bearing and support structure resulting in an opposing sinusoidal load distribution which buckles the spring fingers. The radial load also causes severe deformation of the structure to allow separation of the threads resulting in spanner nut liberation.
More efficient engines that rotate at faster speeds than previous designs create both larger radial loads and larger overturning moments during a fan blade out event. Accordingly, there remains a need for a bearing support structure with a spring finger housing which is lightweight, but is able to withstand the high radial and overturning moment loads of a fan blade out event.